[QUOTE=vineyridge;6047711]
And since there is no bony connection between the scapula and the rest of the horse, the withers as attachment point are crucial.
.[/QUOTE]
No bone or joint as such, but it is certainly attached, and shoulder blade length and slope (effectively largely determines wither set), humerus, and even the top-line all relate to the wither. The wither set even relates to hind length through the top-line but that’s getting a bit advanced for this thread. So many variations in all of this and the effect of the wither that you really do need to apply a very open mind.
The importance of the wither in isolation itself may be questionable, as it appears a horse can break a wither point without it effecting function (Apart from effect acute pain etc). It may be more about what the withers position says about the shoulder blade, back, neck set etc, rather than anything the wither itself does.